A surgical microscope of the kind described above is known from U.S. Pat. No. 5,795,295. This surgical microscope includes an OCT-system (optical coherence tomography) which generates an OCT-scanning beam from laser beam radiation. The OCT-system includes an analyzing unit for evaluating interference signals. The OCT-system includes a device for scanning the OCT-scanning beam and two scan mirrors which can be displaced about two axes of movement. The OCT-scanning beam in the surgical microscope is coupled into the illuminating beam path of the surgical microscope via a divider mirror. The OCT-scanning beam and the illuminating beam are deflected through the microscope main objective to the object region.
The Carl Zeiss Surgical Microscope System OPMI® Visu 200 includes a surgical microscope illuminating module of the kind described above. This illuminating module is configured for attachment to the base body of a surgical microscope. The illuminating module includes an illuminating optic in the form of two lens assemblies which transpose an illuminated field diaphragm into a parallel imaging beam path which runs perpendicularly to the optical axis of the microscope main objective when the illuminating module is connected to the surgical microscope. The field diaphragm is illuminated with light from the light conductor. The illuminating module contains two illuminating mirrors which deflect the illuminating light parallel to the optical axis of the microscope main objective.
An OCT-system (Optical Coherence Tomography) permits the non-invasive illustration and measurement of structures within a tissue utilizing optical coherence tomography. As an image providing process, the optical coherence tomography permits especially section images or volume images of biological tissue to be generated with micrometer resolution. A corresponding OCT-system includes a source for time-dependent incoherent and spatially coherent light having a specific coherence length which is guided to a specimen beam path and a reference beam path. The specimen beam path is directed onto the tissue to be examined. Laser radiation, which is radiated back into the specimen beam path because of scatter centers in the tissue, superposes the OCT-system with laser radiation from the reference beam path. An interference signal results because of the superposition. The position of scatter centers for the laser radiation in the examined tissue can be determined from this interference signal.
For OCT-systems, the building principles of the “time-domain OCT” and of the “Fourier-domain OCT” are known.
The configuration of a “time-domain OCT” is described, for example, in U.S. Pat. No. 5,321,501 with reference to FIG. 1a at column 5, line 40, to column 11, line 10. In a system of this kind, the optical path length of the reference beam path is continuously varied via a rapidly moving reference mirror. The light from specimen beam path and reference beam path is superposed on a photo detector. When the optical path lengths of the specimen and reference beam paths are coincident, then an interference signal is provided on the photo detector.
A “Fourier-domain OCT” is, for example, described in international patent publication WO 2006/100544 A1. To measure the optical path length of a specimen beam path, light from a reference beam path is superposed onto light from a specimen beam path. In contrast to the time-domain OCT, the light from the specimen beam path and reference beam path is not supplied directly to a detector for a measurement of the optical path length of the specimen beam path but is first spectrally dispersed by means of a spectrometer. The spectral intensity of the superposed signal generated in this manner from specimen beam path and reference beam path is then detected by a detector. By evaluating the detector signal, the optical path length of the specimen beam path can be determined.